Ultraviolet absorbents have been blended into various cosmetics largely for the purposes of preventing the product from decomposing due to ultraviolet light and of preventing skin damage (sunblock).
Users with sensitive skin sometimes feel irritation from an ultraviolet absorbent in a cosmetic.
Because of this, a method of alleviating this irritation has been sought after strongly.
The inventors searched many common raw materials suitable for a cosmetic base agent, and discovered that polypropylene glycol, specific polar oils, and polybutylene glycol have a very high efficacy in terms of suppressing skin absorption of an ultraviolet absorbent.
And, the inventors discovered that, by blending said polypropylene glycol or specific polar oils or polybutylene glycol in a cosmetic, the skin irritation of sensitive skin can be alleviated without affecting the effect of the ultraviolet absorbent.
The aforementioned polypropylene glycol, specific polar oils, and polybutylene glycol are inexpensive and provide a good sensation during use, rendering them very preferable from the point of view of cosmetic formulation design. Therefore, the aforementioned alkylene glycol and specific polar oils can be used as superior irritation alleviating agents in cosmetics. The significance of the present invention is greater for sunblock cosmetics in particular, because they contain more than a certain amount of an ultraviolet absorbent.
Conventionally, lipophilic drugs are blended into an endermic liniment. Lipophilic drugs have a high affinity to skin and are easily absorbed through skin. Blending lipophilic drugs into an endermic liniment sometimes causes skin irritation on sensitive skin.
A method that employs a urethane compound has been developed in order to alleviate skin irritation due to retinoic acid (JP-T 7-506109 bulletin).
However, since irritation alleviating agents are expensive, the development of low cost irritation alleviating agents has been strongly desired. Also, the development of irritation alleviating agents with good usability and easy formulation design has been strongly desired.
The object of the present invention is to provide an irritation alleviating agent for lipophilic drugs that is inexpensive, has good usability, and allows easy formulation design.
The inventors conducted earnest research and made a new discovery that blending a substance having a high affinity with lipophilic drugs into an endermic liniment suppresses distribution of the lipophilic drugs into the corneum and irritation is alleviated while the effect of the lipophilic drugs on the skin is maintained. This discovery lead to a discovery that polypropylene glycol and polar oils have a particularly high effect of alleviating irritation due to lipophilic drugs.
Said polypropylene glycol and polar oils, when blended into an endermic liniment, exhibit good usability, low cost, and easy formulation design. Polypropylene glycol was found to be particularly superior in alleviating irritation by retinol.
Also, polybutylene glycol was found to have a high effect of alleviating irritation by lipophilic drugs. Polybutylene glycol, when blended into an endermic liniment, exhibits good usability, lowcost, and easy formulation design.